While inserting a symbol onto a page, the symbol's insertion point is not at the mouse pointer but is one grid point away, to the left, right, top, or bottom depending on which way the mouse is moved. When the design area is clicked to insert the symbol, the symbol is inserted in the correct, desired position.
Similarly, after selecting the start point of a wire, the end point appears to be one grid point away from the mouse cursor until the design area is clicked to select the end point, at which time the endpoint is correct.
Updating the video card driver resolved the issue. In that case, the video card was an ATI Radeon HD460.
Keywords: offset, jump, move, erratic